Today took the P4 out to, fly up to tower on top of Hubbard Park in CT. P4 could not do it. Had plenty of battery & range but because I hit the 400' ceiling I couldn't get up the mountain - would have hit trees. No problem at all making the run with the P3 Pro. I've tried to calibrate the height setting on P4, no success - unless you consider getting it to go lower a success. If there's anyone that has a work around for this please let me know. Otherwise I'm returning the bird to DJI. FYI: everything else works great and I get great time out of the battery. I really hope there is something that can be done to get over the 400' limit.